Applicant's U.S. Pat. No. 5,142,712 describes a vacuum assisted toilet, wherein a vacuum is applied to the toilet bowl outlet during a flushing, so less water is required for a complete flushing. The toilet bowl outlet includes a lower trap, in addition to the usual upper trap, with a trapway extending between them and receiving the vacuum during a flushing. The lower trap is open to the passage of air between flushings, to prevent all water in the toilet bowl from being siphoned out. However, soon after the beginning of a flushing, the lower trap is closed against the passage of air, so the vacuum applied to the trapway can help pull out the contents of the toilet bowl instead of having the vacuum dissipated to the drain or sewer system.
Although the vacuum assisted toilet described in applicant's U.S. Pat. No. 5,142,712 operates fairly well, applicant has experimented with the toilet in an attempt to obtain even better flushings. A better flushing is one which produces a more complete evacuation of the contents of the toilet bowl, using the same or less flush water. In such tests, items that both sink and float in water, such as marbles and plastic balls (of varying densities), are placed in the toilet bowl and the percent of the those items which are removed is measured. A toilet which was constructed to produce better flushings using a small amount of flush water, would be of value.